Student or Learner
I saw that you can use both in and on with islands, but what's the difference?
Well, "in" means "inside boundaries", while "on" means "on the surface of".
Strictly speaking, you use "on" for small islands and "in" for countries -- "in Germany", but "on the Isle of Wight".
But some islands are also countries: Malta is one. So you can say "in Malta" if you are thinking about the country, and "on Malta" if you are thinking about the island. Because they are the same thing, you can choose which you prefer.
With larger island countries, it's more usual to say "in".